T. M. Shaun Johnston 
Scripps Institution of Oceanography
University of California, San Diego
La Jolla, CA, 92093
USA

Tel:    (858) 534 9747
Fax:    (858) 534 8045

My email

Current Position

• I am a postdoctoral researcher in the Physical Oceanography Research Division with Dan Rudnick.  

• We are looking at horizontal mixing by eddies in the mixed layer as part of a CLIVAR Climate Process Team using 66 778 km of SeaSoar data.

• We are creating a SeaSoar database, which will be freely available to all interested researchers.  If you would like to contribute data to this archive, let me know! 
  

Ongoing Work

• Coastal Upwelling
• I was a postdoc in the Ocean Sciences Department at University of California, Santa Cruz with Margaret McManus (now at the University of Hawaii) and participated in the Autonomous Ocean Sampling Network II experiment.  
• On cruises in the summer of 2003 near Monterey Bay during relaxations of upwelling favourable winds, we observed formation of thin layers of phytoplankton at eddies.  Initially broad vertical distributions of chlorophyll are thinned at eddies by 1) vertical shear of horizontal currents and 2) isopycnal compression due to Ekman pumping.  Higher vertical nutrient gradients may lead to higher growth of phytoplankton.
  

 

• By combining objectively mapped shipboard ADCP and CTD data, we are calculating absolute geostrophic currents (Chereskin and Trunnell, 1996; Rudnick and Luyten, 1996).  These are the cross-shore transects (from north to south with locations shown above) through the California Undercurrent.  No level of no motion at 1000 m.

• Internal Tide Scattering
  
  • As a student with Mark Merrifield in the Department of Oceanography at the University of Hawaii and working with Peter Holloway (ADFA, UNSW), we used the Princeton Ocean Model to examine the scattering of the mode 1 internal tide at topography.
  • Large internal tides are generated at the Hawaiian Ridge as seen in the Hawaii Ocean Mixing Experiment.
  • While some of the energy is dissipated locally, most of the energy propagates away from the ridge in low modes.  We showed topographic scattering of the mode 1 internal tide redistributes energy in space, mode number, and frequency.  The energy scattered into higher modes can contribute to abyssal ocean mixing.
  
   
  
  

• T. M. S. Johnston, M. A. Merrifield, and P. E. Holloway, Internal tide scattering at the Line Islands Ridge, J. Geophys. Res., 108 (C11), 10.1029/2003JC001844, 2003.
  
  
• T. M. S. Johnston and M. A. Merrifield, Internal tide scattering at seamounts, ridges, and islands, J. Geophys. Res., 108 (C6), 10.1029/2002JC001528, 2003.

• H. Brix, J. Hench, H. L. Johnson, T. M. S. Johnston, J. Polton, M. Roughan, and P. Testor, An international perspective on postgraduate education in physical oceanography, Oceanography, 16, 128-133, 2003.

• cv.html
  

Deep-Sea Corals

• I was lucky enough to go on a submersible dive amongst some fabulous gold corals at ~400 m near French Frigate Shoals.  From the Hawaii Undersea Research Lab site:
  
  
  
  
• See video (large or small) of this small shrimp (galatheid) hanging out on a gold coral (gerardia sp.) from our Pisces V dive.

• Defence: phdd4.ppt
• Defence (older version): phdd.pdf
• IUGG 2004: iugg.pdf

Revised: 17 November 2004